What do they use in their aircraft? And can this cause problems when they are serviced at European airports?
Not really. Aircraft fasteners aren't just bought from a local hardware shop; they have to have a certification for the product, the manufacturer and even the stockist. Whilst there are "aircraft standard parts catalogues" from which the designer will select things like fasteners the actual parts themselves are very tightly controlled due to the problems of counterfeit parts making their way into the supply chain.
Part of the design process looks at opportunities to standardise parts for improved supportability and reduced through-life cost by reducing what is known as the "logistic footprint", but it's one element of a trade-off. A standardised fastener will usually be larger and heavier than is actually required, and its material may need particular fits or finishes on other parts to avoid corrosion, pick-up or fatigue. It might sound like a trivial amount of extra weight, but there are typically over 100,000 fasteners on a large commercial aeroplane and an extra gramme of weight on each is 100kg or freight lost on every flight (it's the freight that pays for the flights on most routes).
For the military it's about reducing the spares and tools required to operate and support the aeroplane - the russians often use the novel approach of using non-standard head sizes on bolts and AF-sizes on nuts to minimise the numb er of tools needed for deployed operations. The T72 main battle tank could be completely dismantled using six sizes of spanner/socket, three screwdrivers and a couple of special tools!