Non personalised items are usually fulfilled from in-country stock. Personalised items are not fulfilled from regional distribution centres, but are instead despatched from manufacture - in most cases from China.
The global semiconductor shortage, coupled with international shipping delays, are significantly impacting supply chains - and for this reason some items are experiencing delays in order fulfilment.
When placing your order, you should have seen an estimated shipping date; Apple’s estimated dates are generally very accurate. Your order confirmation will have included contact information for any enquiries concerning your order; if you have any concerns at all, you should contact Apple.