Si tu pouvais avoir un million dollars americains, mais …

… is not correct.

In the case of ballpark figures such as "million", "dizaine", "trentaine" etc (as opposed to exact numbers such as "deux", "dix", "soixante" etc), you need to place "de" in between:

un million de chats

une dizaine de chats

une trentaine de chats {vs: trente chats}

des centaines de milliers de chats

There are two problems with million/milliard. On the one hand, they are measure nouns belonging to the same series as dizaine/centaine/millier but contrary to the latter, they act like mètre/litre:

• un mètre de tissu, un mètre cinquante de tissu
• un litre de lait, un litre vingt-cinq de lait
• un million d’euros, un million deux d’euros
• un millier d’euros, ?un millier deux d’euros?

On the other hand, they are cardinal building units (like dix/cent/mille) with the special property of demanding de marked nouns when they stand on the right margin:

• 999 999 pages, un million de pages, un million une pages
• deux milliards cent millions de pages, deux milliards cent millions une page

In the last examples above, they are not measure nouns because the first one is not understood as 2 000 000 100 x millions, and the second one runs into the same problem with the added quirk that the decimal parts have to be masculine.