[calebio]

Not a direct answer to your reuqestion re: questionable activity, but for me it's more about ease of access.

A SIM in the U.S. is significantly more difficult to acquire than a SIM in Mexico/many other countries.

E.g.

- Limit on # of SIMs purchased at retailers, low ability to use cash to purchase them, generally always on camera

- SIMs locked up behind the counter at lots of major retailers in the U.S.

- Activation requirements on U.S. networks for prepaid SIMs

Granted, if you're a company you can certainly acquire a lot of SIMs. A lot of questionable activity uses straw purchases, very similar to folks using smurfs to acquire pseudoephedrine in the 2000s.

[JasonADrury]

Certain internet forums related to VOIP routing seem to have no lack of sellers offering to sell all kinds of US sim cards by the thousands, I don't think availability is an issue.

[calebio]

Historically, availability was very different between the two countries when we're specifically talking about purchasing SIMs for questionable activity.

Physically acquiring the SIMs is only one part of the process as they're pretty worthless without going through the activation process.

Prior to this year in Mexico (which introduced ID-based regulations around SIM purchase/activation), you could buy a SIM at a remote gas station, a data package in cash, and activate it without giving your name/email/etc. Now, in 2026, you have to show an ID/passport to do that.

The U.S. doesn't have a federal regulation (as far as I know) for this. That level of network protection is usually at the provider level. However, activating the SIM almost always requires an email or existing phone number and not just purchase/possession of the SIM+top-up card. Purchasing the top-up card sometimes can be done in cash, other times requires a pre-paid debit which has its own limitations/regulations due to a mix of KYC/AML. But applying said top-up card usually still requires at least some form of identity verification. For some of the top national providers, and I'm not sure what model they use to gauge risk to make this decision, they even require an SSN (for prepaid!) and run some form of a check on you (I'm not entirely sure if it's a soft credit check or what).