If Europe invested more in their militaries they could dictate their own terms with their neighbors.
Also, the U.S. MIC wants to sell to its NATO "allies".
Also, until the 1990s, Western European armies were VERY professional and capable of military and technological innovation.
Hell, the Bundeswehr was well equipped with fairly competitive weaponry made by German manufacturers such as Heckler and Koch, KNDS (Leopard tanks), Rheinmetall, etc