No problem at all! I actually use a Lenovo 65W USB-C power adapter to charge my wife’s 2019 MacBook Air. We had initially thought that using a different brand’s charger might cause issues, but it has been working perfectly fine for us.
The great thing about USB-C power adapters that support USB Power Delivery (USB-PD) is that they are designed to negotiate with the device being charged to provide the appropriate voltage. In other words, the charger and the MacBook Air communicate with each other to figure out the right amount of power to deliver.
Even if the charger you have is more powerful (in terms of wattage) than the original charger that came with the MacBook Air, it shouldn’t pose a problem. The MacBook Air has its own power management system that controls how much current it takes. So, even if the charger can supply more power, the MacBook Air will only draw what it needs.
In my experience, using a 65W USB-C power adapter with the MacBook Air has been seamless. It charges the laptop just as efficiently as the original charger, and we haven’t encountered any issues so far.
To sum up, as long as you have a USB-C power adapter that supports USB Power Delivery and can negotiate the appropriate voltage with the MacBook Air, using a 65W charger should be absolutely fine. The MacBook Air’s power management system will ensure that it takes only the necessary amount of power.