Many advanced systems (such as the F-35, HIMARS, Patriot) have software and hardware that is controlled, updated, or encrypted by the US. This can indirectly act as a "switch," because allies cannot freely reprogram or modify the systems without approval from the US. They could shut down the entire Western defense capability if they wanted to. Most often, Washington limits capacity through policy or hardware configuration prior to transfer (e.g., by limiting the range of HIMARS in Ukraine). It's not a "remote control," but it achieves the same effect. Communications and networks (Link 16, GPS, etc.) are also under US control and can be shut down or restricted in certain areas, giving Washington leverage.
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