The truth is probably somewhere in between your position and the US traditional narrative. French and British orders did pay for a lot of US aircraft factory expansion, but perhaps not as much as some people think it terms of percent. British and French paid for very little shipyard expansion in 1938-39-40. British and French paid for very little small arms production expansion or artillery expansion or even ammo expansion (not saying there were no ammo orders, just not new factories built to handle such orders). Not sure that France was interested in American tanks, Britain was or at least the idea of America building British designed tanks. This idea was flatly rejected by the Americans after the fiasco of WW I production when the US joined the war with all of it's factories tooled up for British and French (and Russian) weapons and the US had to either adopt foreign weapons or do without for months after declaring war. The US was happy to take British money for US designed tanks (with a bit of input from the British.
The whole "America would be forced to go to war in 1942 with a 1938 sized arms industry" bit rather ignores the US Navy re-armament plans. The USS Iowa and New Jersey were both ordered on July 1st 1939 and the Iowa was laid down on June 27th 1940.
It also ignores President Roosevelt's May 16th 1940 speech calling for the US to develop the capacity to built 50,000 planes a year and asked for $896,000,000 total for both air and other items. Congress voted some (most) of the money in June (?) and it was this that funded the Ford plant and the Packard Merlin production in part and a number of other projects/plants.
BTW this was a around 1 1/2 years after...................Jan. 12, 1939, he delivered a special message to Congress calling for strengthening of the Air Corps. Congress then authorized $300 million for 5,500 new airplanes.
It took a while for even the 1939 appropriation to kick in. That included the order for the 560 (524 actual aircraft and 36 as spare parts) P-40s but even the April 27th 1939 order tool a while as the first production P-40 didn't fly until April 4th 1940. Orders were placed for other fighters, bombers, recon and trainers.