> The pro-Israel lobby has spent roughly 10-15M per year... This is hardly enough to offset the billions of dollars spent in U.S. politics

Those $10-15 mil are given to politicians and the billions are spent from US tax payers money.

> For this to be true it would also require Israel to "buy" presidents who acted against Israel's interests

You might want to look into campaign contributions made by AIPAC and similar isreli institutions to these presidents.

> Most (75-90%) of U.S. Federal military aid to Israel is contingent on Israel buying from American companies.

Which effectively makes these weapons free for Israel. US is literally funding Israeli army.