Code for my tutorial about making your Picker's searchable.

SearchablePicker.swift

import SwiftUI

struct SearchBar: UIViewRepresentable {

    @Binding var text: String
    var placeholder: String

    func makeUIView(context: UIViewRepresentableContext<SearchBar>) -> UISearchBar {
        let searchBar = UISearchBar(frame: .zero)
        searchBar.delegate = context.coordinator

        searchBar.placeholder = placeholder
        searchBar.autocapitalizationType = .none
        searchBar.searchBarStyle = .minimal
        return searchBar
    }

    func updateUIView(_ uiView: UISearchBar, context: UIViewRepresentableContext<SearchBar>) {
        uiView.text = text
    }

    func makeCoordinator() -> SearchBar.Coordinator {
        return Coordinator(text: $text)
    }

    class Coordinator: NSObject, UISearchBarDelegate {

        @Binding var text: String

        init(text: Binding<String>) {
            _text = text
        }

        func searchBar(_ searchBar: UISearchBar, textDidChange searchText: String) {
            text = searchText
        }
    }
}

struct FormView: View {

    let countries = ["Brazil", "Canada", "Egypt", "France", "Germany", "United Kingdom"]

    @State private var pickerSelection: String = ""
    @State private var searchTerm: String = ""
    
    var filteredCountries: [String] {
        countries.filter {
            searchTerm.isEmpty ? true : $0.lowercased().contains(searchTerm.lowercased())
        }
    }

    var body: some View {
        NavigationView {
            Form {
                Picker(selection: $pickerSelection, label: Text("")) {
                    SearchBar(text: $searchTerm, placeholder: "Search Countries")
                    ForEach(filteredCountries, id: \.self) { country in
                        Text(country).tag(country)
                    }
                }
            }
        }
    }
}