Leaving aside the fact that this is yet another installment of It's 1939 And The Next Hitler Is About To Invade Poland silliness, Grassley's historical revisionism is remarkable.
In fact, the United States in 1939 had a foreign policy under FDR, one that was increasingly at odds with Chuck Grassley's Republican Party. After Hitler invaded Poland, Roosevelt urged Congress to repeal the Neutrality Act embargo provisions. They finally got around to it a couple months later, over the objections of isolationist Republicans.
Shortly after, isolationist Republicans also tried to block FDR's Lend Lease Act, which supplied our future allies in the war. Most Republicans nationally were against Lend Lease.
The American position was to help the British but not enter the war. In early February 1941 a Gallup poll revealed that 54 percent of Americans were unqualifiedly in favor of Lend-Lease. A further 15 percent were in favor with qualifications such as: "If it doesn't get us into war," or "If the British can give us some security for what we give them." Only 22 percent were unqualifiedly against the President's proposal. When poll participants were asked their party affiliation, the poll revealed a sharp political divide: 69 percent of Democrats were unqualifiedly in favor of Lend-Lease, whereas only 38 percent of Republicans favored the bill without qualification. A poll spokesperson also noted that, "approximately twice as many Republicans" gave "qualified answers as ... Democrats."
Opposition to the Lend-Lease bill was strongest among isolationist Republicans in Congress, who feared that the measure would be "the longest single step this nation has yet taken toward direct involvement in the war abroad." When the House of Representatives finally took a roll call vote on February 9, 1941, the 260 to 165 vote fell largely along party lines. Democrats voted 238 to 25 in favor and Republicans 24 in favor and 135 against.
More proof Republicans might want to knock off the "It's 1939 - Hitler!" stuff -- they were on the wrong side of that debate.