If the US invades a country for joining the CSTO, that's absolutely on the US.
It might be reasonable for the US to be frustrated or disturbed if Mexico joined the CSTO, but being frustrated and disturbed wouldn't justify invading them to replace their government.
It might be reasonable for the US to be frustrated or disturbed if Mexico joined the CSTO, but being frustrated and disturbed wouldn't justify invading them to replace their government.