So, how much is that the case nowadays, in particular for any critical equipment like fighter jets and so forth?
The F-16 is still the backbone or mainstay of the Pakistan Air Force. The reason is the advanced technology and the sheer amount of time the Pakistan Air Force employed to master this platform.
The Pakistan Air Force has 85 F-16s in its inventory. Of those, 75 are operational. The rest of them are either in need of upgrades, spare parts, or new engines. The USA approved the sale of spare parts and some engines during PM IK's visit to the USA. However, I don't know what happened to them because there has been trouble related to PM IK's Russia visit.
The Pakistan Navy had been using a number of Harpoon anti-ship missiles, which are being replaced by more powerful and longer-range Chinese CM-302 missiles.
Apart from the replaceable vintage equipment, Pakistan's military also uses some new supplies. However, I don't think these are very important in terms of technology.
Pakistan's military uses AS/TPS-78/80 surveillance radars. Recently, they bought TPS-77 radars.
The basic trainer, the PAC Super Mushshak, uses US-made sub systems, e.g., the Lycoming engine, Garmin glass cockpit, Hartzell propeller blade, etc.
How much does the Pakistan military depend on (vintage) US equipment nowadays?
My understanding is that dependence on the USA is not Pakistan's military's main problem. Their main problem is that they are trying hard to diversify their resources, which they are not able to do because of
(1) US interference
(2) a lack of reliable suppliers
(3) budgetary constrainst
Example #1 - US Interference
The Pakistan Army urgently needs to replace its helicopter gunships. Their AH1 Cobra helicopters are 35–40 years old.
In 2013, they opted for the American-made Bell AH1Z Viper helicopters. Initially, the US government approved the sale. Later, the delivery was withheld, possibly because of Indian objections. Then they opted for Turkish TAI T-129 helicopters. Again, the Americans withheld the engine license.
Russia is willing to supply any kind of defence equipment. However, the threat of US sanctions is one of the problems Pakistan is unwilling to cope with.
Example #2 - Lack of reliable supplier
As is evident from its dealings with India, Russia is not a reliable spare parts supplier. Russian arms are also very expensive to maintain in the long run. Secondly, Pakistan is traditionally a Western arms user, while India traditionally uses a lot of Russian weapons. India is also strategically very close to Russia. Therefore, there is an inherent risk in using Russian weapons.
China is ready to supply any kind of defence equipment. However, Chinese technology is not mature enough. For instance, in the case of jet fighters, Pakistani consultants are continuously working with Chinese designers to get Pakistan's requirements fulfilled.
Turkey is a trusted partner. However, they don't have all the technology Pakistan needs. I think their products are also expensive.
Italy has been a reliable supplier. However, I suspect that Pakistan is slowly distancing itself from Italy and other EU members because of expense and possible US interference.
Example #3 - Budgetary constraints
In my opinion, F-16s are the main sticking point in Pakistan's reliance on the USA. There is a good reason for that.
The Pakistan Air Force has been using F-16s for more than forty years now. Over the years, they invested a lot of time and money in developing their force-culture, doctrine, training, maintenance facilities, etc. It would possibly take several decades to replace them. It's not only because of budgetary constraints but also the lack of maturity of Chinese or Turkish technology.
Note: Please let me know if any improvement is needed because I haven't used Google much and this is mostly written from my memory.