” Is a non-citizen on US soil not subject to our laws, or am I missing something? (No great legal mind, I.)”
They are subject to SOME if our laws, but not COMPLETELY. For example, a Brit here must drive on the right side of the road, not the left. They cannot Rob people or murder them. To that extent, they are subject to our territorial laws (i.e. the laws of this particular territory). But can they be drafted into the armed forces? Must a tourist pay taxes to our government on income earned in England? Can they be charged with treason? No. Can a foreign tourist get a US passport? No. They owe no allegiance to this country, so are not (completely) subject to our jurisdiction...and thus if Mary Englishchick drops a kid in Disneyland, that kid is NOT a citizen under the terms of the 14th Amendment.