Here is some questions:

1- LHG LTE6 kit, is it available for the USA and It this he highest gain product you have?

2- Does each product have a IMEI? If not, how do you get the SIM to work with the product?

3- Does your LTE products allow for band selection as a priority?

1) It is available in the USA and the highest gain product MikroTik currently has available, but may not have the bands you need. See the PDF.
2) Yes, all modems have an IMEI.
3) You can select which bands but I'm not sure if you can set a priority for each band

@SiB may chime in with this since he is the MikroTik LTE guru.

1) It is available in the USA and the highest gain product MikroTik currently has available, but may not have the bands you need. See the PDF.
2) Yes, all modems have an IMEI.
3) You can select which bands but I'm not sure if you can set a priority for each band

@SiB may chime in with this since he is the MikroTik LTE guru.

1- Awesome...

2- Will the carriers take the IMEI? I ask because researching here, it seems like 2 years (ish) ago, there were issues with carriers.

3- Selecting it is enough. So that's awesome.

@SiB chiming in would be great. It seems you have knowledge on it too though.

I'm really curious to see how much download speeds increase. Is there a number we should expect with it?

Gigair

1- LHG LTE6 kit, is it available for the USA and It this he highest gain product you have?

Yes, RBLHGR but please found the Brochure PDF in offer without modem (not kit) because in it you found a Gain graph.
X = Mhz = Band's and those on + are in front of device. Example USA use 700Mhz who is on minus and LHGR will be better to reach BTS in opposite direction but 800Mhz on front.
Please read this one answer in post: viewtopic.php?f=21&t=131389#p651290
.

2- Does each product have a IMEI? If not, how do you get the SIM to work with the product?

IMEI and Mac Address and TCP/IP stack etc. works.
USA move to eSIM as standard? No one MikroTik LTE modem works with this - only standard SIM.
.

3- Does your LTE products allow for band selection as a priority?

Default policy is LTE>3G>2G in MikroTik modems. You can select as on/off what give you: LTE>3G or LTE>2G or 3G>2G.
Bands you can on/off but priority is via internal algorithm. In my test's the signal is winning and main var to selection.
Remember that you can do CellLock feature on selected Band/eNB/SectorID/Phy. The second ca-band is automatic and dependence from eNB.
.
RogerWilco

3) You can select which bands but I'm not sure if you can set a priority for each band

Last time some one ask me via Telegram in my signature and I do a script who check offline time and >2m we do change to next Band of customer PrioListOfBand=7,1,3 but in next 4x4m be change this bands and if still stuck in offline then B20 and send SMS as notify.
This give info that you can do many scenario via scripts.
.

@SiB may chime in with this since he is the MikroTik LTE guru.

Thx, but this not notify me, I must just search post with "lte" and "@SiB" words.
My guru is mkx

2- Will the carriers take the IMEI? I ask because researching here, it seems like 2 years (ish) ago, there were issues with carriers.

I'm really curious to see how much download speeds increase. Is there a number we should expect with it?

Speed really depends on the carrier and the tower demand. It should get you decent speeds - I get 40Mbps with SXT-LTE (B3, 26km from tower).

Not sure how many American ISPs use IMEI to restrict hardware, probably best to Bing for this.
Telstra in Australia use to modems by IMEI to ones only sold by them. Glad they have that up.

1) It is available in the USA and the highest gain product MikroTik currently has available, but may not have the bands you need. See the PDF.
2) Yes, all modems have an IMEI.
3) You can select which bands but I'm not sure if you can set a priority for each band

@SiB may chime in with this since he is the MikroTik LTE guru.

1- Awesome...

2- Will the carriers take the IMEI? I ask because researching here, it seems like 2 years (ish) ago, there were issues with carriers.

3- Selecting it is enough. So that's awesome.

@SiB chiming in would be great. It seems you have knowledge on it too though.

I'm really curious to see how much download speeds increase. Is there a number we should expect with it?

#2 Generally you have to use a pre-activated SIM. The modem needs to be certified for use with the carrier and the IMEI has to be loaded into the carrier database to qualify for activation. In most cases you cannot activate a new line of service with the modem IMEI. Many use a Cradlepoint or Pepwave IMEI that is already in their database to activate the SIM and then swap the SIM to the Mikrotik.
This works for Verizon, T-Mobile, AT&T. Sprint ties the IMEI to the SIM so you cannot freely swap between devices.

#2 Generally you have to use a pre-activated SIM. The modem needs to be certified for use with the carrier and the IMEI has to be loaded into the carrier database to qualify for activation. In most cases you cannot activate a new line of service with the modem IMEI. Many use a Cradlepoint or Pepwave IMEI that is already in their database to activate the SIM and then swap the SIM to the Mikrotik.
This works for Verizon, T-Mobile, AT&T. Sprint ties the IMEI to the SIM so you cannot freely swap between devices.

Yep this how exactly it is. I just went though this process in November with AT&T and Verizon. At 1st I used carrier specific hotspots then tested both carrier SIMs in LHGR-US kit.